Done properly, a rubber band suspension pretty much eliminates low frequency rumble and 400hz howl. However, if your playing SO loud, you can hit the tonearms resonant frequency if the recording contains enough signal content around 400hz, then you will hear the arm howl.

Thanks alot Scott, I don't really play it that loud, just wondering what it was.
Even if a record isn't playing and I max out my channel volume and have my house output around nine I get this this loud howl.
I'm just interested to know what causes it, have I maxed out all my headroom and this hum is looping and getting louder?